Objective: The objective of this project is to investigate hypotheses related to nutrition and cancer, and cancer chemoprevention. Background: The NHANES I Epidemiologic Followup Survey (NHEFS) is a prospective cohort study created through a systematic followup of persons examined in the NHANES I. NHANES I investigated the health and nutritional status of the United States population and was particularly targeted toward those population groups hypothesized to be at greatest risk of poor health and nutritional deficiency. The survey was carried out on a probability sample of the civilian non-institutional population of the United States from 1971-75. NHANES I included a sociodemographic and medical history, a standardized medical examination, a dietary questionnaire (24-hour recall with a crude 18-question food frequency questionnaire), hematologic and biochemical tests, and anthropometry. Methods: 14,407 men and women aged 25-74 were eligible for inclusion in the NHEFS cohort. Subjects were first traced and interviewed again for the NHEFS in 1981-84, with additional followups conducted in 1986, 1987, and 1992. A total of over 1,800 confirmed cancers have been identified through the 1992 followup. Progress: Although previous analyses have shown that adult weight gain predicted subsequent breast cancer, recent analyses have shown that neither dietary fat intake nor frequency of eating occasions was associated with subsequent weight change. Increased dietary diversity was associated with reduced mortality, including cancer mortality. Ongoing analyses are evaluating the relation of antioxidants to lung cancer, aspirin use to cancer, and bone mineral density to breast cancer.